Hydrophilic and antistatic treatment for polymers

ABSTRACT

A surface modification to impart antistatic and hydrophilic properties to polyurethanes or polyamides by reaction with acrylonitrile and a base.

O Unlted States Patent [151 3,661,627 Schwarz May 9, 1972 [541HYDROPHILIC AND ANTISTATIC TREATMENT FOR POLYMERS References Cited [72]lnventor: Eckhard C. A. Schwarz, Neenah, Wis. UNITED STATES PATENTS [73]Assignee: Kimberly-Clark Corporation, Neenah, 2,959,496 11/1960 Baechler..117/118 Wis. 3,382,090 5/1968 Meisel ..117/47 A [22] Filed: May 1970Primary Examiner-Alfred L. Leavitt [21 APPL NOJ 38,875 AssistantE.\'aminerlanyce A. Bell Attorney-Daniel J. Hanlon, Jr., William D.Herrick and Raymond J. Miller [52] U.S.C1. ..l17/1l8,8/115.5, 117/47 A,

117/62.1,117/138.8 D, 117/138.8 N, 117/161 KP, [57] ABSTRACT 51 I cl7/161 izza Z A surface modification to impart antistatic and hydrophilicproperties to polyurethanes or polyamides by reaction with [58] FieldofSearch ..117/118,47A,62.1, 138.8 D, acrylonitrile andabase 117/138.8N, 161 P, 161 KP; 260/96 R, DIG. 21;

8/ 1 15.5 5 Claims, N0 Drawings H YDROPHILIC AND ANTISTATIC TREATMENTFOR POLYMERS DESCRIPTION OF THE INVENTION This invention relatesgenerally to the treatment of hydrophobic polymers to render themhydrophilic and antistatic at the surface. More particularly theinvention pertains to the use of a bath containing acrylonitrile and abase such as sodium hydroxide or triethylamine to react with the surfaceof hydrophobic polymers imparting hydrophilic and antistatic propertiesthereto.

Polymers such as polyamides, e.g. nylon, and polyurethanes which haveacidic hydrogens have wide utility as fibers, films or foams. However,such products are generally hydrophobic and require treatment to renderthem antistatic. Thus, for applications such as sponges or wipes whereliquid pickup is important or wrapping film where printability is afactor or where the buildup of static charge is a problem, one or moretreatment steps or coatings is generally necessary to provide a usefulproduct. Examples of such processes may be found in U. 5. Pat. Nos.2,900,278; 3,149,000; 3,249,465; and 3,382,090.

It is a primary object of the present invention to provide a singetreatment that will alter the surface properties of such polymers sothat they become both hydrophilic and have good antistatic qualities.

Other objects and advantages of the invention will become apparent uponreading the following detailed description and upon reference to thespecific examples.

While the invention will be described in connection with one or morepreferred embodiments, it will be understood that I do not intend tolimit the invention to those embodiments. On the contrary, I intend tocover all alternatives, modifications, and equivalents as may beincluded within the spirit and scope of the invention as defined by theappended claims.

EXAMPLE I Example I illustrates the effect of the present invention onpolyurethanes. A 5.0 gram film sample of polyurethane which had beenprepared from toluene diisocyanate and polypropylene oxide was stirredfor 3 hours at 90 C in an aqueous bath of 100 ml containing 0.5 gram ofsodium hydroxides Acrylonitrile was added, 5 grams at the start andgrams dropwise over the 3 hour period. The film was washed in distilledwater, and after drying, the contact angle of water was measured at 20.Prior to treatment the contact angle of water for this sample was 45**When brushed with a wool cloth after treatment, the film did not acceptan electrostatic charge.

EXAMPLE [I Example ll demonstrates the applicability of the presentinvention to the treatment of polyamides. Example I was repeated with afilm of polyhexamethyleneadipamide substituted for the polyurethane.After washing and drying, the contact angle of water was measured to be25: The polyhexamethyleneadipamide film, prior to being treated inaccordance with the present invention, had a contact angle of water of65. This treated film also did not accept an electric charge whenbrushed with a wool cloth.

As the above examples illustrate, the present invention involves thepreparation of an aqueous bath containing a base such as sodiumhydroxide and acrylonitrile. While a preferred concentration of base isabout 5 grams per liter of solution, the range of from I to 20 grams perliter is known to provide use ful results. The preferred means foradding acrylonitrile is to start with a concentration of about 50 gramsper liter adding another 100 grams per liter during the course of thereaction. However, the concentration of acrylonitrile may be variedbetween the limits of 20 and 200 grams per liter of solution.

While the temperature of the bath is not critical, it is preferred thatit be heated to provide a reasonable rate of reaction. The preferred temerature to be used is about C with the range of from 70 to 120 Cconsidered to be useful depending upon the desired reaction rate.

Although water is preferred as a matter of convenience as the liquidvehicle for the bath containing the acrylonitrile and base, any liquidcan be used that is essentially a nonsolvent for the polymer base andnonreactive with the bath constituents. Alcohol is an additional exampleof such a material.

It is not intended that the invention be limited to any particulartheory or concept. However, it is believed that cyanoethylation takesplace. Cyanoethylation may be defined as the addition of an X-H group tothe double bond of acrylonitrile, where X is carbon, oxygen, ornitrogen.

Thus it has been demonstrated that the present invention is useful forall hydrophobic polymers having an acidic hydrogen. When treated inaccordance with this invention, such polymers may be printed andotherwise used as films requiring an antistatic behavior. Further, thepolyurethanes of the present invention may be foamed in a conventionalmanner as illustrated, for example, by the aforementioned patents, andused alone or in combination with other materials as wipes or sponges.

The invention is not limited to sodium hydroxide as a base component. Infact, any base known to effect cyanoethylation may be used. Examples ofother such bases include triethylamine, potassium hydroxide, andN-dialkyl aniline.

While the invention has been described with reference to specificexamples, it is not to be restricted thereto. In its broadest aspects,the invention may be variously embodied within the scope of the appendedclaims.

Iclaim:

1. Method of treating polymers characterized by an acidic hydrogen torender them more hydrophilic and antistatic comprising the step ofcontacting said polymer with a composition containing 20 to 200 gramsper liter of solution of acrylonitrile and l to 20 grams per liter ofsolution of a base capable of effecting cyanoethylation, saidcomposition further containing a liquid vehicle which is essentially anonsolvent for the polymer and nonreactive with said acrylonitrile andbase.

2. The method of claim 1 wherein the polymer is selected from the groupconsisting of polyurethanes and polyamides.

3. The method of claim 1 wherein said composition is prepared by addingabout 5 grams of the base per liter of solution to the liquid vehicle,adding about 50 grams of acrylonitrile per liter of solution, and addinganother grams of acrylonitrile per liter of solution during the courseof the reaction.

4. The method of claim 1 wherein the base is selected from the groupconsisting of sodium hydroxide, triethylamine, potassium hydroxide, andN-dialkyl aniline.

5. The method of claim 1 wherein the composition comprises an aqueousbath at an elevated temperature of from 70 C to C.

2. The method of claim 1 wherein the polymer is selected from the groupconsisting of polyurethanes and polyamides.
 3. The method of claim 1wherein said composition is prepared by adding about 5 grams of the baseper liter of solution to the liquid vehicle, adding about 50 grams ofacrylonitrile per liter of solution, and adding another 100 grams ofacrylonitrile per liter of solution during the course of the reaction.4. The method of claim 1 wherein the base is selected from the groupconsisting of sodium hydroxide, triethylamine, potassium hydroxide, andN-dialkyl aniline.
 5. The method of claim 1 wherein the compositioncomprises an aqueous bath at an elevated temperature of from 70* C to120* C.